Answer:
This action category no longer exists in RFEM 6 and RSTAB 9.
It is necessary to create the imperfection cases separately and assign them to the corresponding load case or load combination:
To create an imperfection load case, use the Data navigator (Imperfections → Imperfection Cases → right-click: New Imperfection Case) or directly in the "Load Cases and Combinations" dialog box; see the image.
